The present invention relates to a power transmission device that is installed in a vehicle and provided with a clutch that transmits power from a motor to an axle, and a vehicle having the power transmission device.
This type of power transmission device conventionally has a first hydraulic pump (mechanical oil pump) that drives based on power from an engine; a pressure control valve that controls the force of hydraulic pressure discharged from the first hydraulic pump; a manual shift valve that operates in association with a shift operation; a solenoid valve whose input port is connected to the first hydraulic pump through the manual shift valve; a selector valve that is formed as a two-position electromagnetic valve (and includes a check valve), wherein at a first position the selector valve communicates with an oil passage that is interposed between and connects an output port of the solenoid valve to a friction engaging device (clutch) and at a second position the selector valve cuts off this oil passage; and a second hydraulic pump (electromagnetic pump) that directly delivers discharge pressure to the clutch. (See Japanese Patent Application Publication No. JP-A-2008-180303 for an example.) The proposed device can purportedly reduce energy loss and save energy by delivering pressure oil from the first hydraulic pump through the selector valve during operation of the friction engaging device, which requires a large volume of high-pressure oil, and by delivering pressure oil from the second hydraulic pump when holding this device at a predetermined pressure.